Complex post-traumatic stress disorder—the result of sustained abuse over time—is difficult to diagnose, making it harder for those who suffer from it to move on.

When Emily Durant (not her real name) was eight, her relationship with her mother began to deteriorate. "Something just snapped in her one day, I guess," Emily said. Her once-caring mother suddenly stopped doing dishes, taking out the trash, or even putting trash into the trashcan. Dirty plates piled up in the sink, and then all around the kitchen. By the time eight-year-old Emily realized she had to be the one to clean up, flies and maggots had invaded their kitchen.

An only child living alone with her mother, Emily told me she would come home from school every day to find the living room floor covered with new trash and dirty dishes. If Emily didn't pick them up, that's where they stayed. If she didn't do the laundry, there were no clean clothes. If she didn't heat up microwave dinners, they didn't eat.

The first few times Emily asked for help, she says her mother called her lazy, stupid, and worthless. "I learned within a few months to just stop asking," Emily said. Her mother warned her that if she told anyone about their living conditions, she would be put in foster care with a family that didn't love her, and that her cats would be put to sleep.

The family struggled financially: There were eviction warnings at least every other month, and her mother shared every agonizing detail of the family's bills and debts with her daughter. Emily says her mother withheld dinner and wouldn't let her sleep until her chores were done. Dissatisfied with a cleaning job, she once told Emily to strip naked and lie on the couch. She proceeded to beat her with a plastic hanger.

Living under these conditions wasn't just stressful—it left Emily deeply traumatized, constantly fearing her own safety under her mother's abuse, but without anywhere else to go. She began to develop symptoms of what she now recognizes as trauma.

"Lots of nights, I couldn't fall asleep for hours," she said. "I started having panic attacks pretty frequently at school—at least one a month—and I'd have to ask to go to the restroom or nurse because I thought I was going to pass out or have a stroke or something every time."

She was prescribed antidepressants by eighth grade, but the prescription was never filled (her mother said they couldn't afford it). Although she didn't know it at the time, Emily was developing what many psychiatrists, psychologists, and trauma experts are now calling Complex Post-Traumatic Stress Disorder, or C-PTSD.

Unlike formally recognized PTSD diagnoses, C-PTSD doesn't stem from a singular event, but is instead the result of sustained abuse and powerlessness, from which the victim has little hope of escape.

"C-PTSD occurs when the hyper-vigilance of PTSD is accompanied by a breakdown in the ability to self-regulate," said Julian Ford, a psychology and law professor who heads the Center for Trauma Recovery at the University of Connecticut. "Intense emotions or emotional deadness will overwhelm the person's ability to cope. Mentally, they will suffer lapses in consciousness or in problem solving or judgment. And interpersonally, they will have extreme conflict in or withdraw from relationships."

The distinction between PTSD and C-PTSDwas first introduced by Harvard Medical School professor Judith Herman in her 1992 book Trauma & Recovery. Her research found that the effects of chronic neglect, stress, and subjugation were creating an entire class of people—including survivors of sexual abuse and domestic abuse; persecuted racial, religious, and ethnic groups; and former hostages—whose trauma didn't fit the profile for PTSD diagnoses because it had been sustained over time.

Though Herman introduced the idea of C-PTSD more than 20 years ago, the psychiatric community has been slow to recognize the distinction. C-PTSD was not included in the most recent version of the Diagnostic and Statistical Manual of Mental Disorders, published in 2013. (PTSD, by comparison, has been listed in the DSM since 1980.) The term is only now being added to the World Health Organization's International Classification of Diseases, which is still under revision and won't be finalized until 2018.

A lack of clear and consistent diagnostic criteria mean clinicians are liable to mischaracterize the symptoms of C-PTSD as borderline, dependent, or masochistic personality disorders. And the lack of awareness about C-PTSD means that those who have it, like Emily, often assume they are simply anxious or depressed. The fact that complex trauma often involves children who grew up in abusive households can make the symptoms of C-PTSD seem like a child's personality, rather than the signs of psychological distress.

When Emily was 18, she went to see a therapist. "I was severely depressed," she told me, "to the point of feeling suicidal at times. I had extreme general and social anxiety. Uncontrollable intrusive memories of things that have happened to me over the years would lead to me feeling even more depressed and anxious. I finally realized I needed help."

After a conversation about her childhood, the therapist quickly deduced that depression and anxiety were only part of a larger problem, and told her about C-PTSD. She was lucky—C-PTSD is commonly misdiagnosed, and the symptoms are frequently confused with depression or anxiety, which Emily had been diagnosed with since middle school.

But once she was diagnosed, Emily felt awkward telling people about it. "I don't think most millennials are very familiar with PTSD," Emily said. "It's pretty much only known as 'that thing soldiers get,' and that's about the extent to which most people my age know about it. Complex PTSD is even more unknown."

Because of this lack of awareness, Emily has been reluctant to share her experience. "If anyone asks, I generally just tell them I have depression and anxiety, just because it's too hard to explain what C-PTSD entails."

Ford, the University of Connecticut psychologist, agrees that C-PTSD, like many mental illnesses, is often minimized, which can be frustrating for those dealing with the aftermath of trauma.

"It is a popular misconception that simply learning to relax, meditate, think rationally, or have a healthy, active lifestyle will reverse the stress reactivity caused by C-PTSD," he said. "Those positive psychology approaches are only beneficial for people with C-PTSD after they have first mastered the skill of shifting their brain and body from survival mode to a state of calm confidence."

For Emily, that shift has already begun. Since she moved out of her mother's house two years ago at the age of 18, she's used therapy to work through her trauma and hopes that as C-PTSD becomes more widely accepted, others won't have to suffer in silence for as long as she did.